Methods of using drilling fluid compositions with enhanced rheology

ABSTRACT

Drilling fluid compositions include a base fluid, at least one additive chosen from an emulsifier, weighting material, fluid-loss additive, viscosifier, or alkali compound, and from 0.1 wt. % to 1 wt. %, based on total weight of the drilling fluid composition, of an ethoxylated alcohol compound having the formula R—(OCH2CH2)7—OH, in which R is a saturated or unsaturated, linear or branched hydrocarbyl group having from 8 to 20 carbon atoms. The base fluid may be an aqueous base fluid. Methods for drilling a subterranean well include operating a drill in a wellbore in the presence of a drilling fluid composition including the base fluid, the additive, and the ethoxylated alcohol compound.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 16/037,493 filed Jul. 17, 2018, which claimspriority to U.S. patent application Ser. No. 15/485,724, filed Apr. 12,2017, which claims the benefit of priority to U.S. Provisional PatentApplication Ser. No. 62/454,189, filed Feb. 3, 2017 (SA 6100 MA), and toU.S. Provisional Patent Application Ser. No. 62/454,192 filed Feb. 3,2017 (SA 6101 MA), which are incorporated by reference in thisdisclosure in their entirety.

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to drilling fluidcompositions for drilling oil wells and to methods of drillingsubterranean wells using the drilling fluid compositions. In particular,the present disclosure relates to drilling fluid compositions havingrheology enhancing compounds and to methods of drilling subterraneanwells using the drilling fluid compositions.

BACKGROUND

During drilling operations, a drilling fluid, which may also be referredto as drilling mud, is circulated through the wellbore to cool the drillbit, to convey rock cuttings to the surface, or to support the wellboreagainst collapse of the wellbore and against intrusion of fluids fromthe formation, among other purposes. Drilling fluids are formulated tohave certain fluid characteristics, such as density and rheology, forexample, that allow the drilling fluid to perform these functions.However, under certain extreme downhole conditions, such as excessivetemperature, for example, some of the properties of the drilling fluidmay be altered. For example, the drilling fluid may thicken, increase inviscosity, or form a gel. These changes in properties of the drillingfluid can lead to problems such as solids settling, stuck pipes, andexcessive pump pressure.

Drillers counteract these issues by adding thinners, which are sometimesreferred to as mud thinners, to the drilling fluid. Some of the morecommon drilling fluid thinners include plant tannins, such as quebracho,lignosulfonic acid and its salts (e.g., chromium, iron, cobalt, sodium,and aluminum salts or any mixture of these salts), lignitic materials,and polyphosphates. Certain synthetic polymers have also been used asthinners for drilling fluids. However, there is an ongoing need fordrilling fluid thinners and/or additives that are capable ofwithstanding extreme downhole conditions.

SUMMARY

Embodiments of the present disclosure are directed to drilling fluidcompositions comprising an ethoxylated alcohol compound and to methodsfor drilling a subterranean well using the drilling fluid compositionshaving the ethoxylated alcohol compound.

According to one or more embodiments, a drilling fluid compositionincludes a base fluid, at least one additive chosen from an emulsifier,a weighting material, a fluid-loss additive, a viscosifier, or an alkalicompound, and from 0.1 weight percent (wt. %) to 1 wt. %, based on thetotal weight of the drilling fluid composition, of an ethoxylatedalcohol compound having formula (I):

R—(OCH₂CH₂)₇—OH   (I)

where R is a hydrocarbyl group having from 8 to 20 carbon atoms.

In some embodiments, the drilling fluid compositions may have yieldpoints from 45 pounds of force per 100 square feet (lbf/100 ft²) (21.6pascals (Pa)) to 100 lbf/100 ft² (48 Pa) and a 10-second gel strengthsfrom 1 lbf/100 ft² (0.5 Pa) to 30 lbf/100 ft² (14.4 Pa) as determinedaccording to test methods provided in API RP 13B-1. In example drillingfluid compositions, the base fluid is an aqueous base fluid. In otherexample drilling fluid compositions, the base fluid is an aqueous basefluid that comprises at least 50 weight percent water based on the totalweight of the aqueous base fluid. The aqueous base is chosen from freshwater, filtered water, distilled water, sea water, salt water, producedwater, formation brine, or combinations thereof.

In some example drilling fluids, R is a saturated linear hydrocarbylgroup. In other example drilling fluid compositions, R is —(CH₂)_(m)CH₃,where m is 11, 12, or 13. In other example drilling fluid compositions,R has exactly 12 carbon atoms. The drilling fluid composition may have adensity of equal to or greater than 70 pounds of mass per cubic foot(lbm/ft³).

In some example drilling fluid compositions, the at least one additivecomprises a weighting material. The weighting material is chosen from atleast one of barite, calcium carbonate, hematite, siderite, or ilmenite.

In some examples, the drilling fluid composition includes from 20 wt. %to 50 wt. % base fluid, based on the total weight of the drilling fluidcomposition. The drilling fluid may include from 1 wt. % to 73 wt. %weighting material based on the total weight of the drilling fluidcomposition. The drilling fluid composition may optionally include from0.01 wt. % to 0.7 wt. % xanthan gum polymer based on the total weight ofthe drilling fluid composition. The drilling fluid composition mayoptionally include from 0.01 wt. % to 0.7 wt. % soda ash based on thetotal weight of the drilling fluid composition. The drilling fluidcomposition may optionally include from 0.01 wt. % to 3 wt. % sodiumsulfite based on the total weight of the drilling fluid composition. Thedrilling fluid composition may optionally include from 0.1 wt. % to 1wt. % starch based on the total weight of the drilling fluidcomposition.

According to one or more other embodiments, a method of drilling asubterranean well includes operating a drill in a wellbore in thepresence of a drilling fluid composition comprising a base fluid, atleast one additive chosen from an emulsifier, a weighting material, afluid-loss additive, a viscosifier, or an alkali compound, and from 0.1wt. % to 1 wt. %, based on the total weight of the drilling fluidcomposition, of an ethoxylated alcohol compound having formula (I):

R—(OCH₂CH₂)₇—OH   (I)

where R is a hydrocarbyl group having from 8 to 20 carbon atoms. In someembodiments, the drilling fluid composition has a yield point of from 45lbf/100 ft² (21.6 Pa) to 100 lbf/100 ft² (48 Pa) and a 10-second gelstrength of from 1 lbf/100 ft² (0.5 Pa) to 30 lbf/100 ft² (14.4 Pa) asdetermined according to test methods provided in API RP 13B-1 (AmericanPetroleum Institute Recommended Procedure 13B-1). The base fluid may bean aqueous base fluid. In some example methods, the base fluid is anaqueous base fluid comprising at least 50 weight percent water based onthe total weight of the aqueous base fluid. In example methods, thedrilling fluid composition further comprises one or more of a xanthangum polymer, soda ash, sodium sulfite, or starch.

Additional features and advantages of the described embodiments will beset forth in the detailed description which follows, and in part will bereadily apparent to those skilled in the art from that description orrecognized by practicing the described embodiments, including thedetailed description which follows and the claims.

DETAILED DESCRIPTION

To drill a subterranean well or wellbore, a drill string including adrill bit and drill collars to weight the drill bit is inserted into apredrilled hole and rotated to cause the drill bit to cut into the rockat the bottom of the hole, producing rock cuttings. To remove the rockcuttings from the bottom of the wellbore, a drilling fluid is pumpeddown through the drill string to the drill bit. The drilling fluid coolsthe drill bit and lifts the rock cuttings away from the drill bit. Thedrilling fluid carries the rock cuttings upwards as the drilling fluidis recirculated back to the surface. At the surface, the rock cuttingsare removed from the drilling fluid, and the drilling fluid is thenrecirculated back down the drill string to the bottom of the wellbore.The term “rock cuttings” is intended to include any fragments, pieces,or particulates separated from the formation by the drill bit orotherwise present in the wellbore.

Under certain extreme downhole conditions, such as excessive temperatureor difficult formations, some of the properties of conventional drillingfluids may be altered. For example, interaction of the drilling fluidwith a formation having swelling clay and/or excessive solids content orsubjecting the drilling fluid to extreme downhole temperatures may causethe conventional drilling fluid to thicken, excessively increase inviscosity, undergo gelation, or any combination of these. In somedrilling scenarios, conventional drilling fluids having an increaseddensity and, therefore, increased solids content may enable drilling ofa pressurized formation or may be used to control and kill a flowingdownhole formation. The increased concentration of solids and increaseddensity of the conventional drilling fluids used in these applicationsincrease the ability of the drilling fluids to support the wellbore andprovide enhanced hydrostatic pressure to prevent fluids in the formationfrom flowing into the wellbore. However, in these challenging scenarios,the increased density and increased solid content of the conventionaldrilling fluids can lead to problems such as solids settling, stuckpipes, and excessive pump pressure.

The drilling fluid compositions described in this disclosure serveseveral functions in the drilling process. The drilling fluidcompositions provide lubrication and cooling to the drill bit. Accordingto embodiments, the drilling fluid compositions also aid with cleaningthe wellbore by transporting rock cuttings from the drill bit to thesurface. Additionally, in embodiments, the drilling fluid compositionsprovide hydrostatic pressure in the wellbore to provide support to thesidewalls of the wellbore and prevent the sidewalls from collapsing andcaving-in on the drill string. In embodiments, the drilling fluidcompositions provide hydrostatic pressure in the wellbore to preventfluids in the downhole formations from flowing into the wellbore duringdrilling operations.

Embodiments of the present disclosure are directed to drilling fluidcompositions having a rheology enhancing compound. The rheologyenhancing compound is an ethoxylated alcohol compound having thechemical formula R—(OCH₂CH₂)₇—OH, where R is a saturated or unsaturated,linear or branched hydrocarbyl group having from 8 to 20 carbon atoms.An example drilling fluid composition incorporating the ethoxylatedalcohol compound includes a base fluid, one or more additives includingemulsifiers, weighting material, fluid-loss additives, viscosifiers, oralkali compounds, and from 0.1 weight percent (wt. %) to 1 wt. %, basedon the total weight of the drilling fluid composition, of theethoxylated alcohol compound having formula (I):

R—(OCH₂CH₂)₇—OH   (I)

where R is a saturated or unsaturated, linear or branched hydrocarbylgroup having from 8 to 20 carbon atoms. In some embodiments, thedrilling fluid composition with the ethoxylated alcohol compound mayhave a yield point of from 45 pounds of force per 100 square feet(lbf/100 ft²) (21.6 Pa) to 100 lbf/100 ft² (48 Pa) and a 10-second gelstrength of from 1 lbf/100 ft² (0.5 Pa) to 30 lbf/100 ft² (14.4 Pa),where 1 lbf/100 ft² is approximately 0.48 Pascal (Pa).

Without intent to be bound by theory, it is believed that the presenceof the ethoxylated alcohol compound in the drilling fluid compositionmodifies the rheology of the drilling fluid composition by creating athinning effect in the drilling fluid composition while maintaining thehole-cleaning abilities of the drilling fluid composition. The thinningeffect is believed to reduce the gel strength of the drilling fluidcomposition, so as to improve pump-ability and prevent stuck-pipeproblems. However, the yield point and the density of the drilling fluidcomposition having the ethoxylated alcohol compound are maintainedcompared to a comparative drilling fluid composition in which anequivalent weight of water is substituted in place of the ethoxylatedalcohol compound. Yield point and density are related to the ability ofa drilling fluid composition to convey rock cuttings to the surface(hole-cleaning ability). Maintenance of the yield point and density ofthe drilling fluid composition having the ethoxylated alcohol compoundpreserves this ability of the drilling fluid composition to convey rockcuttings to the surface.

The drilling fluid compositions having the ethoxylated alcohol compoundshave specific properties and characteristics, including density,viscosity, solids content, pump-ability, and hole-cleaning capability,that improve handling of the drilling fluid compositions during drillingoperations and preserve the ability of the drilling fluid compositionsto convey the rock cuttings from the bottom of the wellbore to thesurface. In particular, the drilling fluid compositions having theethoxylated alcohol compound exhibit specific rheological propertiesthat enable the drilling fluid composition to be pumped down through thedrill string while also enabling the drilling fluid compositions toconvey the rock cuttings from drill bit to the top of the wellbore. Therheological properties of the drilling fluid compositions having theethoxylated alcohol compound may reduce or eliminate drilling problemssuch as solids settling, stuck pipes, and excessive pump pressure.Additionally, the drilling fluid compositions having the ethoxylatedalcohol compounds have sufficient density to provide the hydrostaticpressure necessary to support the sidewalls of the wellbore and preventfluids in the formation from flowing into the wellbore.

The drilling fluid compositions according to embodiments may includeweighting material added to a base fluid, such as water or oil forexample, and the ethoxylated alcohol compound. Other additives may beadded to the drilling fluid composition to influence or modify thedensity, rheology, or other properties of the drilling fluid. Theethoxylated alcohol compound may be a reaction product of a fattyalcohol ethoxylated with ethylene oxide at a 7:1 molar ratio of thefatty alcohol to the ethylene oxide. Ethylene oxide is a cyclic etherhaving the chemical formula C₂H₄O and may be produced through oxidationof ethylene in the presence of a silver catalyst.

The fatty alcohols used as the reactant to make the ethoxylated alcoholcompound include alcohols having formula R—OH, in which R is a saturatedor unsaturated, linear, or branched hydrocarbyl group having from 8 to20 carbon atoms, such as from 8 to 18 carbon atoms, from 8 to 16 carbonatoms, from 8 to 14 carbon atoms, from 8 to 12 carbon atoms, from 8 to10 carbon atoms, from 10 to 20 carbon atoms, from 10 to 18 carbon atoms,from 10 to 16 carbon atoms, from 10 to 14 carbon atoms, from 10 to 12carbon atoms, from 12 to 20 carbon atoms, from 12 to 18 carbon atoms,from 12 to 16 carbon atoms, from 12 to 14 carbon atoms, from 14 to 20carbon atoms, from 14 to 18 carbon atoms, from 14 to 16 carbon atoms,from 16 to 20 carbon atoms, or 12 carbon atoms. As used in thisdisclosure, a “hydrocarbyl group” refers to a hydrocarbon radical formedby removing one hydrogen atom from a hydrocarbon compound consisting ofcarbon atoms and hydrogen atoms. The hydrocarbyl group forms a chemicalbond with another chemical group at the carbon atom of the hydrocarbylgroup from which the hydrogen atom was removed. In one or moreembodiments, R of the fatty alcohol may be a saturated linearhydrocarbyl group. Alternatively, R of the fatty alcohol may be abranched hydrocarbyl group.

The fatty alcohol having formula R—OH may be a naturally derived fattyalcohol or a synthetically derived fatty alcohol. The fatty alcohol maybe a naturally-occurring fatty alcohol, such as a fatty alcohol obtainedfrom natural sources such as animal fats or vegetable oils. The fattyalcohol may also be a hydrogenated naturally-occurring unsaturated fattyalcohol. Alternatively, the fatty alcohol may be a synthetic fattyalcohol prepared from a petroleum source or other source through one ormore synthesis reactions. Non-limiting examples of fatty alcohols mayinclude, but are not limited to capryl alcohol, perlargonic alcohol,decanol (decyl alcohol), undecanol, dodecanol (lauryl alcohol),tridecanol (tridecyl alcohol), myristyl alcohol (1-tetradecanol),pentadecanol (pentadecyl alcohol), cetyl alcohol, palmitoeyl alcohol(cis-9-hexadecenol), heptadecanol (heptadecyl alcohol), stearyl alcohol,nonadecyl alcohol, arachidyl alcohol, alcohol ethoxylates, othernaturally-occurring fatty alcohols, other synthetic fatty alcohols, orcombinations of any of these fatty alcohols. In examples, the fattyalcohol may be produced through oligomerization of ethylene derived froma petroleum source, or in other examples, the fatty alcohol may beproduced through hydroformylation of alkenes followed by hydrogenationof the hydroformylation reaction product. In one or more embodiments,the fatty alcohol may include a hydrocarbon chain (R) having from 12 to14 carbon atoms. Some example ethoxylated alcohol compounds may be madeusing a saturated linear fatty alcohol having a saturated linearhydrocarbyl group R with 12 carbon atoms.

The ethoxylated alcohol compound may be made by reacting the fattyalcohol with ethylene oxide at a 7:1 molar ratio of the fatty alcohol tothe ethylene oxide. The ethoxylation reaction may be conducted at anelevated temperature and in the presence of an anionic catalyst, such aspotassium hydroxide (KOH) for example. The ethoxylation reactionproceeds according to the following Equation 1.

$\begin{matrix}{{{ROH} + {7\; C_{2}H_{4}O}}\overset{\mspace{20mu} {KOH}\mspace{20mu}}{\rightarrow}{{R\left( {{OCH}_{2}{CH}_{2}} \right)}_{7}{OH}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In Equation 1, R is the hydrocarbon portion of the fatty alcoholpreviously described in this disclosure. As shown in Equation 1, thereaction product may have the general chemical formula R—(OCH₂CH₂)₇—OH,where R is a saturated or unsaturated, linear or branched hydrocarbylgroup having from 8 to 20 carbon atoms, such as from 8 to 18 carbonatoms, from 8 to 16 carbon atoms, from 8 to 14 carbon atoms, from 8 to12 carbon atoms, from 8 to 10 carbon atoms, from 10 to 20 carbon atoms,from 20 to 18 carbon atoms, from 10 to 16 carbon atoms, from 10 to 14carbon atoms, from 10 to 12 carbon atoms, from 12 to 20 carbon atoms,from 12 to 18 carbon atoms, from 12 to 16 carbon atoms, from 12 to 14carbon atoms, from 14 to 20 carbon atoms, from 14 to 18 carbon atoms,from 14 to 16 carbon atoms, from 16 to 20 carbon atoms, or 13 carbonatoms. In embodiments, R is —(CH₂)_(m)CH₃ where m is from 7 to 19, from9 to 15, or from 11 to 13. In some embodiments, m is 11, 12, or 13. Insome embodiments, the ethoxylated alcohol compound produced fromethoxylation of the fatty alcohol with ethylene oxide at a 7:1 molarratio of fatty alcohol to ethylene oxide has the chemical formulaCH₃(CH₂)_(m)(OCH₂CH₂)₇—OH; where m is an integer from 11 to 13. In someembodiments, m is 11. In some embodiments, the ethoxylated alcoholcompound comprises, consists essentially of, or consists of a compoundhaving the chemical formula CH₃(CH₂)₁₁(OCH₂CH₂)₇—OH. In someembodiments, the fatty alcohol may be a fatty alcohol ethoxylate havingformula R—(OCH₂CH₂)_(n)—OH, in which n is less than 7. In theseembodiments, the fatty alcohol ethoxylate may be further ethoxylatedwith ethylene oxide to produce the ethoxylated alcohol compound havingformula R—(OCH₂CH₂)₇—OH.

It should be understood that unreacted fatty alcohol, unreacted ethyleneoxide, one or more other alcohol ethoxylates having the formulaR—(OCH₂CH₂)_(n)—OH in which “n” is an integer greater than or less than7, other byproducts, or combinations of these compounds may be presentas impurities in the ethoxylated alcohol left over from its synthesis.Therefore, the drilling fluid composition may contain small amounts ofunreacted fatty alcohols, unreacted ethylene oxide, one or more otheralcohol ethoxylates having the formula R—(OCH₂CH₂)_(n)—OH in which “n”is an integer greater than or less than 7, other byproducts, orcombinations of these compounds. As used in this disclosure, the term“small amount” refers a quantity than 2% by weight based on the totalweight of a composition. For example, the ethoxylated alcohol compoundmay include from 0.001 wt. % to 2 wt. % unreacted fatty alcohols,unreacted ethylene oxide, one or more alcohol ethoxylates having theformula R—(OCH₂CH₂)_(n)—OH in which “n” is an integer greater than orless than 7, other byproducts, or combinations of these components,based on the total weight of the ethoxylated alcohol compound. Theweight percent of the ethoxylated alcohol compound in the drilling fluidcomposition does not include the weight of impurities or byproducts,such as the unreacted fatty alcohols, unreacted ethylene oxide, one ormore other alcohol ethoxylates having the formula R—(OCH₂CH₂)_(n)—OH inwhich “n” is an integer greater than or less than 7, other byproducts,or combinations of these components.

As previously discussed, the drilling fluid composition includes atleast a base fluid, the ethoxylated alcohol compound, and one or moreadditives, any or all of which may change one or more characteristics ofthe drilling fluid composition. The base fluid may include water, oil(natural or synthetic), or a water/oil emulsion. For drilling fluidcompositions that are water-based, the base fluid may be an aqueous basefluid. An aqueous base fluid may be any suitable fluid such as water ora solution containing both water and one or more organic or inorganiccompounds dissolved in the water or otherwise completely miscible withthe water. For example, in some embodiments, the aqueous base fluid mayinclude at least 50 wt. % water. The aqueous base fluid may include oneor more of fresh water, well water, filtered water, distilled water, seawater, salt water, produced water, formation brine, other type of water,or combinations of waters. Alternatively, the drilling fluidcompositions may be oil-based and may have a base fluid that is anatural oil or synthetic oil. The base fluid of the drilling fluidcomposition may also be a water-in-oil emulsion or an invert emulsion.In water-in-oil emulsions and invert emulsions, oil is a continuousphase and water is dispersed in the continuous oil phase byemulsification so that the drilling fluid does not have a distinct waterlayer.

The drilling fluid composition may have an amount of the base fluidsufficient to enable the drilling fluid composition to be circulated tothe drill bit at the bottom of a wellbore and back to the surface. Thedrilling fluid composition may include from 20 wt. % to 99 wt. % basefluid based on the total weight of the drilling fluid composition. Forexample, the drilling fluid composition may have from 20 wt. % to 80 wt.%, from 20 wt. % to 70 wt. %, from 20 wt. % to 60 wt. %, from 20 wt. %to 50 wt. %, from 20 wt. % to 40 wt. %, from 23 wt. % to 99 wt. %, from23 wt. % to 80 wt. %, from 23 wt. % to 70 wt. %, from 23 wt. % to 60 wt.%, from 23 wt. % to 50 wt. %, from 23 wt. % to 40 wt. %, from 24 wt. %to 99 wt. %, from 24 wt. % to 80 wt. %, from 24 wt. % to 70 wt. %, from24 wt. % to 60 wt. %, from 24 wt. % to 50 wt. %, from 24 wt. % to 40 wt.%, from 25 wt. % to 99 wt. %, from 25 wt. % to 80 wt. %, from 25 wt. %to 70 wt. %, from 25 wt. % to 60 wt. %, from 25 wt. % to 50 wt. %, orfrom 25 wt. % to 40 wt. % base fluid based on the total weight of thedrilling fluid composition. Alternatively, the drilling fluidcomposition may include from 170 pounds of mass per barrel of oil(lbm/bbl) to 340 lbm/bbl base fluid based on the total volume of thedrilling fluid composition. For example, in embodiments, the drillingfluid composition may have from 170 lbm/bbl to 330 lbm/bbl, from 170lbm/bbl to 310 lbm/bbl, from 170 lbm/bbl to 280 lbm/bbl, from 170lbm/bbl to 250 lbm/bbl, from 170 lbm.bbl to 220 lbm/bbl, from 170lbm/bbl to 210 lbm/bbl, from 185 lbm/bbl to 340 lbm/bbl, from 185lbm/bbl to 330 lbm/bbl, from 185 lbm/bbl to 310 lbm/bbl, from 185lbm/bbl to 280 lbm/bbl, from 185 lbm/bbl to 250 lbm/bbl, from 185lbm.bbl to 220 lbm/bbl, from 200 lbm/bbl to 340 lbm/bbl, from 200lbm/bbl to 330 lbm/bbl, from 200 lbm/bbl to 310 lbm/bbl, from 200lbm/bbl to 280 lbm/bbl, from 200 lbm/bbl to 250 lbm/bbl, from 210lbm/bbl to 340 lbm/bbl, from 210 lbm/bbl to 330 lbm/bbl, from 210lbm/bbl to 310 lbm/bbl, from 210 lbm/bbl to 280 lbm/bbl, from 210lbm/bbl to 250 lbm/bbl, from 220 lbm.bbl to 340 lbm/bbl, from 220lbm/bbl to 330 lbm/bbl, from 220 lbm/bbl to 310 lbm/bbl, from 220lbm/bbl to 280 lbm/bbl, from 250 lbm/bbl to 340 lbm/bbl, or from 250lbm/bbl to 310 lbm/bbl base fluid based on the total volume of thedrilling fluid composition. In embodiments, the drilling fluidcomposition may have from 20 wt. % to 50 wt. % base fluid based on thetotal weight of the drilling fluid composition. In other embodiments,the drilling fluid composition may have from 25 wt. % to 50 wt. % basefluid based on the total weight of the drilling fluid composition.

In embodiments, the drilling fluid composition may include a weightingmaterial. In some embodiments, the weighting material may be aparticulate solid having a specific gravity (SG) sufficient to increasethe density of the drilling fluid composition by a certain amountwithout adding so much weighting material that the drilling fluidcomposition cannot be circulated through the wellbore. The weightingmaterial may have a specific gravity (SG) of from 2 grams per cubiccentimeter (g/cm³) to 6 g/cm³. Examples of weighting materials include,but are not limited to, barite (minimum SG of 4.20 g/cm³), hematite(minimum SG of 5.05 g/cm³), calcium carbonate (minimum SG of 2.7-2.8g/cm³), siderite (minimum SG of 3.8 g/cm³), ilmenite (minimum SG of 4.6g/cm³), other weighting materials, or any combination of these weightingmaterials. Some example drilling fluid compositions may include bariteas the solid.

The drilling fluid composition may include a weight percent of weightingmaterial sufficient to increase the density of the drilling fluidcomposition to allow the drilling fluid composition to support thewellbore and prevent fluids in downhole formations from flowing into thewellbore. In embodiments, the drilling fluid composition may includefrom 1 wt. % to 80 wt. % weighting material based on the total weight ofthe drilling fluid composition. In some embodiments, the drilling fluidcomposition may include from 1 wt. % to 75 wt. %, from 1 wt. % to 74 wt.%, from 1 wt. % to 73 wt. %, from 1 wt. % to 70 wt. %, from 1 wt. % to60 wt. %, from 20 wt. % to 80 wt. %, from 20 wt. % to 75 wt. %, from 20wt. % to 74 wt. %, from 20 wt. % to 73 wt. %, from 20 wt. % to 70 wt. %,from 20 wt. % to 60 wt. %, from 50 wt. % to 80 wt. %, from 50 wt. % to75 wt. %, from 50 wt. % to 74 wt. %, from 50 wt. % to 73 wt. %, from 50wt. % to 70 wt. %, from 50 wt. % to 60 wt. %, from 60 wt. % to 80 wt. %,or from 60 wt. % to 75 wt. % weighting material based on the totalweight of the drilling fluid composition. In embodiments, the drillingfluid composition may include from 2 lbm/bbl to 750 lbm/bbl weightingmaterial based on the total volume of the drilling fluid composition. Insome embodiments, the drilling fluid composition may include from 2lbm/bbl to 650 lbm/bbl, from 2 lbm/bbl to 550 lbm/bbl, from 2 lbm/bbl to450 lbm/bbl, from 2 lbm/bbl to 300 lbm/bbl, from 50 lbm/bbl to 750lbm/bbl, from 50 lbm/bbl to 650 lbm/bbl, from 50 lbm/bbl to 550 lbm/bbl,from 50 lbm/bbl to 450 lbm/bbl, from 50 lbm/bbl to 300 lbm/bbl, from 100lbm/bbl to 750 lbm/bbl, from 100 lbm/bbl to 650 lbm/bbl, from 100lbm/bbl to 550 lbm/bbl, from 100 lbm/bbl to 450 lbm/bbl, from 100lbm/bbl to 300 lbm/bbl, from 300 lbm/bbl to 750 lbm/bbl, or from 300lbm/bbl to 650 lbm/bbl weighting material, based on the total volume ofthe drilling fluid composition.

The drilling fluid composition may include at least one solid-phasecomponent. Examples of solid-phase components in the drilling fluidcompositions may include, but are not limited to, the weightingmaterials, starch, soda ash, bentonite, lime, sodium sulfite, othersolid-phase component, or combinations of these solid-phase components.All of the solid-phase components together make up a total solidscontent of the drilling fluid composition. In some embodiments, thedrilling fluid composition may have a total solids content of equal toor greater than 50 wt. % based on the total weight of the drilling fluidcomposition. Alternatively, in other embodiments, the drilling fluidcomposition may have a solids content of equal to or greater than 60 wt.% based on the total weight of the drilling fluid composition.

The drilling fluid compositions may have an amount of the ethoxylatedalcohol compound sufficient to produce a thinning effect in the drillingfluid composition while maintaining the hole-cleaning ability of thedrilling fluid composition. In particular, in embodiments, the drillingfluid composition may have an amount of the ethoxylated alcohol compoundsufficient to reduce the gel strength of the drilling fluid compositionwhile maintaining the yield point of the drilling fluid composition. Insome embodiments, the drilling fluid composition may have an amount ofthe ethoxylated alcohol compound sufficient to reduce the 10-second gelstrength into a range from 1 lbf/100 ft² (0.5 Pa) to 30 lbf/100 ft²(14.4 Pa) while maintaining the yield point of the drilling fluidcomposition in a range of from 45 lbf/100 ft² (21.6 Pa) to 100 lbf/100ft² (14.4 Pa). In embodiments, the drilling fluid composition mayinclude from 0.1 wt. % to 1 wt. % ethoxylated alcohol compound havingformula (I), based on the total weight of the drilling fluidcomposition. In other embodiments, the drilling fluid composition mayinclude from 0.1 wt. % to 0.8 wt. %, from 0.1 wt. % to 0.6 wt. %, from0.1 wt. % to 0.5 wt. %, from 0.2 wt. % to 1 wt. %, from 0.2 wt. % to 0.8wt. %, from 0.2 wt. % to 0.6 wt. %, from 0.2 wt. % to 0.5 wt. %, from0.3 wt. % to 1 wt. %, from 0.3 wt. % to 0.8 wt. %, from 0.3 wt. % to 0.6wt. %, or from 0.3 wt. % to 0.5 wt. % ethoxylated alcohol compoundhaving chemical formula (I) based on the total weight of the drillingfluid. In embodiments, the drilling fluid composition may include from 1lbm/bbl to 20 lbm/bbl ethoxylated alcohol compound having formula (I),based on the total volume of the drilling fluid composition. Inembodiments, the drilling fluid composition may have from 1 lbm/bbl to17 lbm/bbl, from 1 lbm/bbl to 14 lbm/bbl, from 1 lbm/bbl to 10 lbm/bbl,from 2 lbm/bbl to 20 lbm/bbl, from 2 lbm/bbl to 17 lbm/bbl, from 2lbm/bbl to 14 lbm/bbl, from 2 lbm/bbl to 10 lbm/bbl, from 5 lbm/bbl to20 lbm/bbl, from 5 lbm/bbl to 17 lbm/bbl, from 5 lbm/bbl to 14 lbm/bbl,from 5 lbm/bbl to 10 lbm/bbl, from 10 lbm/bbl to 20 lbm/bbl, from 10lbm/bbl to 17 lbm/bbl, or from 10 lbm/bbl to 14 lbm/bbl ethoxylatedalcohol compound having formula (I), based on the total volume of thedrilling fluid composition.

The drilling fluid compositions may optionally include one or aplurality of additives to enhance the properties and characteristics ofthe drilling fluid composition. Examples of the additives include, butare not limited to, emulsifiers, fluid-loss control additives,viscosifiers (viscosity control agents), alkali compounds, orcombinations of these. The drilling fluid composition may alsooptionally include pH buffers, electrolytes, glycols, glycerols,dispersion aids, corrosion inhibitors, defoamers, and other additives orcombinations of additives. In embodiments, the drilling fluidcomposition may optionally include a viscosifier to impart non-Newtonianfluid rheology to the drilling fluid composition to facilitate liftingand conveying rock cuttings to the surface of the wellbore. Examples ofviscosifiers may include, but are not limited to, a xanthan gum polymersuch as XC polymer, bentonite, polyacrylamide, polyanionic cellulose, orcombinations of these viscosifiers. In some embodiments, the drillingfluid composition may optionally include a xanthan gum polymer known asXC polymer, which is a polysaccharide secreted by the bacteriaXanthomonas campestris (XC). Drilling fluid compositions that includexanthan gum polymer may exhibit flat velocity profiles of the drillingfluid composition subjected to annular flow. The flat velocity profileresulting from the presence of the xanthan gum polymer in the drillingfluid composition may improve the efficiency of the drilling fluidcomposition in lifting and conveying rock cuttings to the surface. Anexample drilling fluid composition may optionally include from 0.01 wt.% to 0.7 wt. % xanthan gum polymer based on the total weight of thedrilling fluid composition. In other embodiments, drilling fluidcomposition may optionally include from 0.01 wt. % to 0.5 wt. %, from0.01 wt. % to 0.3 wt. %, from 0.01 wt. % to 0.1 wt. %, from 0.01 wt. %to 0.05 wt. %, from 0.05 wt. % to 0.7 wt. %, from 0.05 wt. % to 0.5 wt.%, from 0.05 wt. % to 0.3 wt. %, from 0.05 wt. % to 0.1 wt. %, from 0.1wt. % to 0.7 wt. %, from 0.1 wt. % to 0.5 wt. %, from 0.1 wt. % to 0.3wt. %, from 0.3 wt. % to 0.7 wt. %, from 0.3 wt. % to 0.5 wt. %, or from0.5 wt. % to 0.7 wt. % xanthan gum polymer, based on the total weight ofthe drilling fluid composition. Unless otherwise stated, the weightpercent of an additive in the drilling fluid composition is based on thetotal weight of the drilling fluid composition. An example drillingfluid composition may optionally include from 0.1 lbm/bbl to 25 lbm/bblxanthan gum polymer based on the total volume of the drilling fluidcomposition. In other embodiments, the drilling fluid composition mayoptionally include from 0.1 lbm/bbl to 20 lbm/bbl, from 0.1 lbm/bbl to15 lbm/bbl, from 0.1 lbm/bbl to 10 lbm/bbl, from 0.1 lbm/bbl to 5lbm/bbl, from 1 lbm/bbl to 25 lbm/bbl, from 1 lbm/bbl to 20 lbm/bbl,from 1 lbm/bbl to 15 lbm/bbl, from 1 lbm/bbl to 10 lbm/bbl, from 1lbm/bbl to 5 lbm/bbl, from 5 lbm/bbl to 25 lbm/bbl, from 5 lbm/bbl to 20lbm/bbl, from 5 lbm/bbl to 15 lbm/bbl, from 5 lbm/bbl to 10 lbm/bbl,from 10 lbm/bbl to 25 lbm/bbl, from 10 lbm/bbl to 20 lbm/bbl, from 10lbm/bbl to 15 lbm/bbl, or from 15 lbm/bbl to 25 lbm/bbl xanthan gumpolymer, based on the total volume of the drilling fluid composition. Insome embodiments, the drilling fluid composition may optionally includefrom 0.01 wt. % to 3 wt. % bentonite, based on the total weight of thedrilling fluid composition. In other embodiments, the drilling fluidcomposition may optionally include from 0.01 wt. % to 2 wt. %, from 0.01wt. % to 1 wt. %, from 0.01 wt. % to 0.5 wt. %, from 0.01 wt. % to 0.1wt. %, from 0.01 wt. % to 0.05 wt. %, from 0.05 wt. % to 3 wt. %, from0.05 wt. % to 2 wt. %, from 0.05 wt. % to 1 wt. %, from 0.05 wt. % to0.5 wt. %, from 0.05 wt. % to 0.1 wt. %, from 0.1 wt. % to 3 wt. %, from0.1 wt. % to 2 wt. %, from 0.1 wt. % to 1 wt. %, from 0.1 wt. % to 0.5wt. %, from 0.5 wt. % to 3 wt. %, from 0.5 wt. % to 2 wt. %, from 0.5wt. % to 1 wt. %, from 1 wt. % to 3 wt. %, from 1 wt. % to 2 wt. %, orfrom 2 wt. % to 3 wt. % bentonite, based on the total weight of thedrilling fluid composition. In some embodiments, the drilling fluidcomposition may optionally include from 0.5 lbm/bbl to 25 lbm/bblbentonite, based on the total volume of the drilling fluid composition.In other embodiments, the drilling fluid composition may optionallyinclude from 0.5 lbm/bbl to 20 lbm/bbl, from 0.5 lbm/bbl to 15 lbm/bbl,from 0.5 lbm/bbl to 10 lbm/bbl, from 0.5 lbm/bbl to 5 lbm/bbl, from 1lbm/bbl to 25 lbm/bbl, from 1 lbm/bbl to 20 lbm/bbl, from 1 lbm/bbl to15 lbm/bbl, from 1 lbm/bbl to 10 lbm/bbl, from 1 lbm/bbl to 5 lbm/bbl,from 5 lbm/bbl to 25 lbm/bbl, from 5 lbm/bbl to 20 lbm/bbl, from 5lbm/bbl to 15 lbm/bbl, from 5 lbm/bbl to 10 lbm/bbl, from 10 lbm/bbl to25 lbm/bbl, from 10 lbm/bbl to 20 lbm/bbl, from 10 lbm/bbl to 15lbm/bbl, or from 15 lbm/bbl to 25 lbm/bbl bentonite, based on the totalvolume of the drilling fluid composition. The drilling fluid compositionmay optionally include other suitable viscosifiers without deviatingfrom the scope of the present subject matter.

The drilling fluid composition may optionally include at least one pHadjuster. In embodiments, the drilling fluid composition may optionallyinclude at least one alkali compound. Examples of alkali compounds mayinclude, but are not limited to, lime (calcium hydroxide, calcium oxide,or a mixture of both), soda ash (sodium carbonate), sodium hydroxide,potassium hydroxide, other strong bases, or combinations of these alkalicompounds. The alkali compounds may react with gases, such as CO₂ or H₂Sfor example, encountered by the drilling fluid composition duringdrilling operations to prevent the gases from hydrolyzing components ofthe drilling fluid composition. Some example drilling fluid compositionsmay optionally include from 0.01 wt. % to 0.7 wt. % soda ash. In otherembodiments, the drilling fluid composition may optionally include from0.01 wt. % to 0.5 wt. %, from 0.01 wt. % to 0.3 wt. %, from 0.01 wt. %to 0.1 wt. %, from 0.01 wt. % to 0.05 wt. %, from 0.05 wt. % to 0.7 wt.%, from 0.05 wt. % to 0.5 wt. %, from 0.05 wt. % to 0.3 wt. %, from 0.05wt. % to 0.1 wt. %, from 0.1 wt. % to 0.7 wt. %, from 0.1 wt. % to 0.5wt. %, from 0.1 wt. % to 0.3 wt. %, from 0.3 wt. % to 0.7 wt. %, from0.3 wt. % to 0.5 wt. %, or from 0.5 wt. % to 0.7 wt. % soda ash, basedon the total weight of the drilling fluid composition. Some exampledrilling fluid compositions may optionally include from 0.1 lbm/bbl to10 lbm/bbl soda ash, based on the total volume of the drilling fluidcomposition. In other embodiments, the drilling fluid composition mayoptionally include from 0.1 lbm/bbl to 8 lbm/bbl, from 0.1 lbm/bbl to 6lbm/bbl, from 0.1 lbm/bbl to 4 lbm/bbl, from 1 lbm/bbl to 10 lbm/bbl,from 1 lbm/bbl to 8 lbm/bbl, from 1 lbm/bbl to 6 lbm/bbl, from 1 lbm/bblto 4 lbm/bbl, from 2 lbm/bbl to 10 lbm/bbl, from 2 lbm/bbl to 8 lbm/bbl,from 2 lbm/bbl to 6 lbm/bbl, from 2 lbm/bbl to 4 lbm/bbl, or from 4lbm/bbl to 10 lbm/bbl soda ash, based on the total volume of thedrilling fluid composition. Other example drilling fluid compositionsmay optionally include from 0.01 wt. % to 3 wt. % lime. In otherembodiments, the drilling fluid composition may optionally include from0.01 wt. % to 2 wt. %, from 0.01 wt. % to 1 wt. %, from 0.01 wt. % to0.5 wt. %, from 0.01 wt. % to 0.1 wt. %, from 0.01 wt. % to 0.05 wt. %,from 0.05 wt. % to 3 wt. %, from 0.05 wt. % to 2 wt. %, from 0.05 wt. %to 1 wt. %, from 0.05 wt. % to 0.5 wt. %, from 0.05 wt. % to 0.1 wt. %,from 0.1 wt. % to 3 wt. %, from 0.1 wt. % to 2 wt. %, from 0.1 wt. % to1 wt. %, from 0.1 wt. % to 0.5 wt. %, from 0.5 wt. % to 3 wt. %, from0.5 wt. % to 2 wt. %, from 0.5 wt. % to 1 wt. %, from 1 wt. % to 3 wt.%, from 1 wt. % to 2 wt. %, or from 2 wt. % to 3 wt. % lime, based onthe total weight of the drilling fluid composition. In other examples,the drilling fluid compositions may optionally include from 0.1 lbm/bblto 10 lbm/bbl lime, based on the total volume of the drilling fluidcomposition. In other embodiments, the drilling fluid composition mayoptionally include from 0.1 lbm/bbl to 8 lbm/bbl, from 0.1 lbm/bbl to 6lbm/bbl, from 0.1 lbm/bbl to 4 lbm/bbl, from 1 lbm/bbl to 10 lbm/bbl,from 1 lbm/bbl to 8 lbm/bbl, from 1 lbm/bbl to 6 lbm/bbl, from 1 lbm/bblto 4 lbm/bbl, from 2 lbm/bbl to 10 lbm/bbl, from 2 lbm/bbl to 8 lbm/bbl,from 2 lbm/bbl to 6 lbm/bbl, from 2 lbm/bbl to 4 lbm/bbl, or from 4lbm/bbl to 10 lbm/bbl lime, based on the total volume of the drillingfluid composition. In embodiments, the drilling fluid composition mayhave a pH of from 9.5 to 12, 9.5 to 11.5, from 9.5 to 11, from 9.5 to10.5, from 9.5 to 10, from 10 to 12, from 10 to 11.5, from 10 to 11,from 10 to 10.5, from 10.5 to 12, from 10.5 to 11.5, from 10.5 to 11,from 11 to 12, from 11 to 11.5, or from 11.5 to 12. In some embodiments,the drilling fluid composition may have a pH of from 9.5 to 10.5.

In some embodiments, the drilling fluid composition may optionallyinclude from 0.01 wt. % to 3 wt. % sodium sulfite. In other embodiments,the drilling fluid composition may optionally include from 0.01 wt. % to2 wt. %, from 0.01 wt. % to 1 wt. %, from 0.01 wt. % to 0.5 wt. %, from0.01 wt. % to 0.1 wt. %, from 0.01 wt. % to 0.05 wt. %, from 0.05 wt. %to 3 wt. %, from 0.05 wt. % to 2 wt. %, from 0.05 wt. % to 1 wt. %, from0.05 wt. % to 0.5 wt. %, from 0.05 wt. % to 0.1 wt. %, from 0.1 wt. % to3 wt. %, from 0.1 wt. % to 2 wt. %, from 0.1 wt. % to 1 wt. %, from 0.1wt. % to 0.5 wt. %, from 0.5 wt. % to 3 wt. %, from 0.5 wt. % to 2 wt.%, from 0.5 wt. % to 1 wt. %, from 1 wt. % to 3 wt. %, from 1 wt. % to 2wt. %, or from 2 wt. % to 3 wt. % sodium sulfite, based on the totalweight of the drilling fluid composition. In some embodiments, thedrilling fluid composition may optionally include from 0.1 lbm/bbl to 10lbm/bbl sodium sulfite, based on the total volume of the drilling fluidcomposition. In other embodiments, the drilling fluid composition mayoptionally include from 0.1 lbm/bbl to 8 lbm/bbl, from 0.1 lbm/bbl to 6lbm/bbl, from 0.1 lbm/bbl to 4 lbm/bbl, from 1 lbm/bbl to 10 lbm/bbl,from 1 lbm/bbl to 8 lbm/bbl, from 1 lbm/bbl to 6 lbm/bbl, from 1 lbm/bblto 4 lbm/bbl, from 2 lbm/bbl to 10 lbm/bbl, from 2 lbm/bbl to 8 lbm/bbl,from 2 lbm/bbl to 6 lbm/bbl, from 2 lbm/bbl to 4 lbm/bbl, or from 4lbm/bbl to 10 lbm/bbl sodium sulfite, based on the total volume of thedrilling fluid composition. In some embodiments, the drilling fluidcomposition may optionally include from 0.1 wt. % to 1 wt. % starch. Inother embodiments, the drilling fluid composition may optionally includefrom 0.1 wt. % to 0.8 wt. %, from 0.1 wt. % to 0.6 wt. %, from 0.1 wt. %to 0.4 wt. %, from 0.2 wt. % to 1 wt. %, from 0.2 wt. % to 0.8 wt. %,from 0.2 wt. % to 0.6 wt. %, from 0.2 wt. % to 0.4 wt. %, from 0.4 wt. %to 1 wt. %, from 0.4 wt. % to 0.8 wt. %, from 0.4 wt. % to 0.6 wt. %,from 0.6 wt. % to 1 wt. %, or from 0.6 wt. % to 0.8 wt. % starch, basedon the total weight of the drilling fluid composition. In someembodiments, the drilling fluid composition may optionally include from0.1 lbm/bbl to 10 lbm/bbl starch, based on the total volume of thedrilling fluid composition. In other embodiments, the drilling fluidcomposition may optionally include from 0.1 lbm/bbl to 8 lbm/bbl, from0.1 lbm/bbl to 6 lbm/bbl, from 0.1 lbm/bbl to 4 lbm/bbl, from 1 lbm/bblto 10 lbm/bbl, from 1 lbm/bbl to 8 lbm/bbl, from 1 lbm/bbl to 6 lbm/bbl,from 1 lbm/bbl to 4 lbm/bbl, from 2 lbm/bbl to 10 lbm/bbl, from 2lbm/bbl to 8 lbm/bbl, from 2 lbm/bbl to 6 lbm/bbl, from 2 lbm/bbl to 4lbm/bbl, or from 4 lbm/bbl to 10 lbm/bbl starch, based on the totalvolume of the drilling fluid composition.

The drilling fluid composition may have a density of from 70 pounds ofmass per cubic foot (lbm/ft³) to 160 lbm/ft³, from 70 lbm/ft³ to 150lbm/ft³, from 70 lbm/ft³ to 140 lbm/ft³, from 70 lbm/ft³ to 130 lbm/ft³,from 70 lbm/ft³ to 120 lbm/ft³, from 70 lbm/ft³ to 110 lbm/ft³, from 70lbm/ft³ to 90 lbm/ft³, from 90 lbm/ft³ to 160 lbm/ft³, from 90 lbm/ft³to 150 lbm/ft³, 90 lbm/ft³ to 140 lbm/ft³, from 90 lbm/ft³ to 130lbm/ft³, from 90 lbm/ft³ to 120 lbm/ft³, from 90 lbm/ft³ to 110 lbm/ft³,from 110 lbm/ft³ to 160 lbm/ft³, from 110 lbm/ft³ to 150 lbm/ft³, from110 lbm/ft³ to 140 lbm/ft³, from 110 lbm/ft³ to 130 lbm/ft³, from 110lbm/ft³ to 120 lbm/ft³, from 120 lbm/ft³ to 160 lbm/ft³, from 120lbm/ft³ to 150 lbm/ft³, or from 120 lbm/ft³ to 140 lbm/ft³, where 1lbm/ft³ is approximately 16.02 kilograms per cubic meter (kg/m³). Someexample drilling fluid compositions may have a density that is equal toor greater than 70 lbm/ft³ (1,602 kg/m³). Other example drilling fluidcompositions may have a density that is equal to or greater than 100lbm/ft³ (1,602 kg/m³). Still other example drilling fluid compositionsmay have a density that is equal to or greater than 120 lbm/ft³ (1,922kg/m³). Still other example drilling fluid compositions may have adensity of from 120 lbm/ft³ (1,922 kg/m³) to 160 lbm/ft³ (2,563 kg/m³).

In one or more embodiments, a drilling fluid composition comprises thebase fluid, one or more additives including emulsifiers, weightingmaterial, fluid-loss additives, viscosifiers, or alkali compounds, andfrom 0.1 wt. % to 1 wt. % of the ethoxylated alcohol compound having thechemical formula R—(OCH₂CH₂)₇—OH, where R is a saturated linearhydrocarbyl having from 8 to 20 carbon atoms. The drilling fluidcomposition may have a yield point of from 45 lbf/100 ft² to 100 lbf/100ft² and a 10-second gel strength of from 1 lbf/100 ft² to 30 lbf/100 ft²as determined according to test methods provided in the AmericanPetroleum Institute (API) Recommended Practice For Field TestingWater-Based Drilling Fluids (RP 13B-1/ISO 10414-1:2002) published August2014 and incorporated by reference into this disclosure in its entirety.In some embodiments, the drilling fluid composition may include from 1wt. % to 73 wt. % of a weighting material, from 0.1 wt. % to 1.0 wt. %soda ash, from 0.01 wt. % to 0.1 wt. % pre-hydrated bentonite, from 0.01wt. % to 0.1 wt. % xanthan gum polymer, from 0.1 wt. % to 1.0 wt. %starch from 0.01 wt. % to 0.1 wt. % lime, and from 0.01 wt. % to 0.1 wt.% sodium sulfite. In some embodiments, the balance of the drilling fluidcomposition is the base fluid.

The ethoxylated alcohol compound produces a thinning effect whencombined with the drilling fluid composition. As previously described,the thinning effect may result in a reduction in the gel strength of thedrilling fluid composition, combined with maintenance of a yield pointof the drilling fluid composition. The viscosity of the drilling fluidcompositions may be measured using a standard oilfield viscometer, suchas a FANN® Model 35 viscometer manufactured by Fann Instrument Companyfor example, according to test methods provided in the API RecommendedPractice For Field Testing Water-Based Drilling Fluids (RP 13B-1/ISO10414-1:2002). The viscosity is reported as shear stress in units ofpounds of force per 100 square feet (lbf/100 ft²). The viscometer mayalso be used to measure the shear rate of the drilling fluidcompositions.

As previously stated, the ethoxylated alcohol compound reduces the gelstrength of the drilling fluid compositions according to embodiments.The gel strength refers to the shear stress of the drilling fluidcomposition measured at a low shear rate following a defined period oftime during which the drilling fluid composition is maintained in astatic state. The shear stress of the drilling fluid composition at lowshear rate may be measured using a standard oilfield viscometer, such asa FANN® Model 35 viscometer operated at low rpms, such as at 3 rpm or 6rpm, according to the test methods described in API Recommended PracticeFor Field Testing Water-Based Drilling Fluids (RP 13B-1/ISO10414-1:2002). To measure the gel strength, the drilling fluidcomposition is first stirred by contacting the drilling fluidcomposition with the spindle of the viscometer and operating theviscometer at 600 rotations per minute (rpm). The viscometer is thenturned off for period of time (time period). For a 10-second gelstrength, the time period is 10 seconds, and for a 10 minute gelstrength, the time period is 10 minutes. It should be understood thatother time periods for measuring gel strength may be used as referencetimes for measurements of gel strength. During the time period, thedrilling fluid composition comes to rest in a static state. Uponexpiration of the time period, the viscometer is turned back on at a lowspeed, such as 3 rpm for example, to generate a low shear rate. Theviscometer reading is then taken. The gel strength of the drilling fluidcomposition is reported in units of pounds of force per 100 square feet(lbf/100 ft²).

The drilling fluid compositions that include the ethoxylated alcoholcompound, may have a 10-second gel strength of less than or equal to 30lbf/100 ft², less than or equal to 25 lbf/100 ft², or less than or equalto 20 lbf/100 ft². In some embodiments, the drilling fluid compositionshaving the ethoxylated alcohol compound may have a 10-second gelstrength of from 1 lbf/100 ft² to 30 lbf/100 ft², from 1 lbf/100 ft² to25 lbf/100 ft², from 1 lbf/100 ft² to 20 lbf/100 ft², from 1 lbf/100 ft²to 15 lbf/100 ft², from 5 lbf/100 ft² to 30 lbf/100 ft², from 5 lbf/100ft² to 25 lbf/100 ft², from 5 lbf/100 ft² to 20 lbf/100 ft², from 5lbf/100 ft² to 15 lbf/100 ft², from 10 lbf/100 ft², to 30 lbf/100 ft²,from 10 lbf/100 ft² to 25 lbf/100 ft², from 10 lbf/100 ft² to 20 lbf/100ft², from 10 lbf/100 ft² to 15 lbf/100 ft², or from 1 lbf/100 ft² to 10lbf/100 ft². In one or more embodiments, the drilling fluid compositionshaving the ethoxylated alcohol compound may have a 10-second gelstrength of from 5 lbf/100 ft² to 25 lbf/100 ft². Alternatively, inother embodiments, the drilling fluid compositions having theethoxylated alcohol compound may have a 10-second gel strength of from 5lbf/100 ft² to 20 lbf/100 ft². The 10-second gel strength of thedrilling fluid composition having the ethoxylated alcohol compound maybe compared to a 10-second gel strength of a comparative drilling fluidin which an equivalent weight of water is substituted for theethoxylated alcohol compound. The 10-second gel strength of the drillingfluid composition having the ethoxylated alcohol compound may be lessthan or equal to 90% of the 10-second gel strength of the comparativedrilling fluid, or less than or equal to 80% of the 10-second gelstrength of the comparative drilling fluid, or less than or equal to 70%of the 10-second gel strength of the comparative drilling fluid.

The drilling fluid composition that include the ethoxylated alcoholcompound, may have a 10 minute gel strength of less than or equal to 60lbf/100 ft², less than or equal to 55 lbf/100 ft², or less than or equalto 50 lbf/100 ft². In some embodiments, the drilling fluid compositionhaving the ethoxylated alcohol compound may have a 10-second gelstrength of from 10 lbf/100 ft² to 60 lbf/100 ft², from 10 lbf/100 ft²to 55 lbf/100 ft², from 10 lbf/100 ft² to 50 lbf/100 ft², from 10lbf/100 ft² to 45 lbf/100 ft², from 20 lbf/100 ft² to 60 lbf/100 ft²,from 20 lbf/100 ft² to 55 lbf/100 ft², from 20 lbf/100 ft² to 50 lbf/100ft², from 20 lbf/100 ft² to 45 lbf/100 ft², from 30 lbf/100 ft² to 60lbf/100 ft², from 30 lbf/100 ft² to 55 lbf/100 ft², from 30 lbf/100 ft²to 50 lbf/100 ft², from 30 lbf/100 ft² to 45 lbf/100 ft², or from 10lbf/100 ft² to 40 lbf/100 ft². In one or more embodiments, the drillingfluid composition having the ethoxylated alcohol compound may have a10-minute gel strength of from 10 lbf/100 ft² to 55 lbf/100 ft².Alternatively, in other embodiments, the drilling fluid compositionhaving the ethoxylated alcohol compound may have a 10-minute gelstrength of from 20 lbf/100 ft² to 50 lbf/100 ft².

The rheology of drilling fluid compositions that include the ethoxylatedalcohol compound may be modeled based on Bingham plastic flow behavior.In particular, the drilling fluid composition having the ethoxylatedalcohol compound behaves as a rigid body at low stress but flows as aviscous fluid at higher shear stress. The rheological behavior of thedrilling fluid composition may be determined by measuring the shearstress on the drilling fluid composition at different shear rates, whichmay be accomplished by measuring the shear stress and/or shear rate onthe drilling fluid composition using a FANN® Model 35 viscometeroperated at 3 rpm, 6 rpm, 100 rpm, 200 rpm, 300 rpm, or 600 rpm, forexample. The rheology of the drilling fluid composition may be evaluatedfrom the plastic viscosity (PV) and the yield point (YP), which areparameters from the Bingham plastic rheology model. The PV is related tothe resistance of the drilling fluid composition to flow due tomechanical interaction between the solids of the drilling fluidcomposition and represents the viscosity of the drilling fluidcomposition extrapolated to infinite shear rate. The PV reflects thetype and concentration of the solids in the drilling fluid composition,and a lesser PV is preferred. The PV of the drilling fluid compositionmay be estimated by measuring the shear stress of the drilling fluidusing a FANN® Model 35 viscometer at spindle speeds of 300 rotations perminute (rpm) and 600 rpm and subtracting the 300 rpm viscositymeasurement from the 600 rpm viscosity measurement according to Equation2, which is subsequently provided. The PV values determined for thedrilling fluid compositions are provided in this disclosure in units ofcentipoise (cP).

PV=(viscosity at 600 rpm)−(viscosity at 300 rpm)   Equation 2

The YP represents the shear stress below which the drilling fluidcomposition behaves as a rigid body and above which the drilling fluidcomposition flows as a viscous fluid. In other words, the YP representsthe amount of stress required to move the drilling fluid compositionfrom a static condition. The YP of a drilling fluid composition iscorrelated with the capacity of the drilling fluid composition to carryrock cuttings through the annulus, which in simplified terms indicatesthe drilling fluid composition's hole-cleaning ability. YP of equal toor greater than 15 lbf/100 ft² is considered acceptable for drilling.The YP is determined by extrapolating the Bingham plastic rheology modelto a shear rate of zero. The YP of the drilling fluid composition may beestimated from the PV from Equation 2 by subtracting the PV fromEquation 2 from the shear stress of the drilling fluid measured at 300rpm according to Equation 3 provided subsequently.

YP=(300 rpm reading)−PV   Equation 3

The YP is expressed as a force per area, such as pounds of force per onehundred square feet (lbf/100 ft²) for example. The methods for measuringand determining PV and YP for the drilling fluid compositions having theethoxylated alcohol compound are consistent with methods conventionallyused for drilling fluids in general.

The drilling fluid compositions having ethoxylated alcohol compounds mayhave a PV of from 45 cP to 100 cP, from 45 cP to 80 cP, from 45 cP to 70cP, from 50 cP to 100 cP, from 50 cP to 80 cP, from 50 cP to 70 cP, from55 cP to 100 cP, from 55 cP to 80 cP, or from 55 cP to 70 cP. In someembodiments, the drilling fluid composition having the ethoxylatedalcohol compound may have a PV of from 45 cP to 80 cP. Alternatively, insome embodiments, the drilling fluid composition having the ethoxylatedalcohol compound may have a PV of from 50 cP to 70 cP. The PV of thedrilling fluid composition having the ethoxylated alcohol compound maybe compared to a PV of a comparative drilling fluid in which anequivalent weight of water is substituted for the ethoxylated alcoholcompound. A difference between the PV of the drilling fluid compositionhaving the ethoxylated alcohol compound and the PV of the comparativedrilling fluid may be equal to or less than 10% of the PV of thecomparative drilling fluid.

The drilling fluid compositions having ethoxylated alcohol compounds asdiscussed previously in this disclosure may have a YP of from 45 lbf/100ft² to 100 lbf/100 ft², from 45 lbf/100 ft² to 80 lbf/100 ft², from 45lbf/100 ft² to 70 lbf/100 ft², from 50 lbf/100 ft² to 100 lbf/100 ft²,from 50 lbf/100 ft² to 80 lbf/100 ft², from 50 lbf/100 ft² to 70 lbf/100ft², from 55 lbf/100 ft² to 100 lbf/100 ft², from 55 lbf/100 ft² to 80lbf/100 ft², or from 55 lbf/100 ft² to 70 lbf/100 ft². In someembodiments, the drilling fluid composition having the ethoxylatedalcohol compound may have a YP of from 45 lbf/100 ft² to 80 lbf/100 ft².Alternatively, in some embodiments, the drilling fluid compositionhaving the ethoxylated alcohol compound may have a YP of from 50 lbf/100ft² to 70 lbf/100 ft². The YP of the drilling fluid composition havingthe ethoxylated alcohol compound may be compared to a YP of thecomparative drilling fluid described above having the ethoxylatedalcohol compound substituted by an equivalent weight of water. Adifference between the YP of the drilling fluid composition having theethoxylated alcohol compound and the YP of the comparative drillingfluid may be equal to or less than 25% of the PV of the comparativedrilling fluid, or less than 20% of the PV of the comparative drillingfluid, or less than 15% of the PV of the comparative drilling fluid.

In one example, a drilling fluid composition comprising from 0.1 wt. %to 1 wt. % of the ethoxylated alcohol compound may have a YP of from 45lbf/100 ft² to 100 lbf/100 ft² and a 10-second gel strength of from 1lbf/100 ft² to 30 lbf/100 ft². In another example, a drilling fluidcomposition comprising the ethoxylated alcohol compound may have a YP offrom 50 lbf/100 ft² to 80 lbf/100 ft² and a 10-second gel strength offrom 5 lbf/100 ft² to 25 lbf/100 ft². In other examples, the drillingfluid composition having the ethoxylated alcohol compound may have a10-second gel strength that is less than or equal to 10% of the10-second gel strength of the comparative drilling fluid described abovehaving the ethoxylated alcohol compound substituted by an equivalentweight of water, and a difference between the YP of the drilling fluidcomposition having the ethoxylated alcohol compound and the YP of thecomparative drilling fluid may be less than or equal to 25% of the YP ofthe comparative drilling fluid.

The drilling fluid composition having the ethoxylated alcohol compoundexhibits a deflocculant effect believed to be attributable to thepresence of the ethoxylated alcohol compound. The deflocculant effect atleast partially counteracts the thickening, excessive viscosity, andgelation of the drilling fluid composition that might occur due tointeraction of the drilling fluid composition with the formation havingswelling clay, excessive solids content, or both or due to extremedownhole temperatures. Specifically, the deflocculating effect exhibitedby the drilling fluid composition having the ethoxylated alcoholcompound works to decrease the gel strength and plastic viscosity of thedrilling fluid composition while maintaining the yield point and thedensity of the drilling fluid composition. The decrease in gel strengthand plastic viscosity of the drilling fluid composition caused by thedeflocculant effect may result in a decrease in the pump pressurerequired to deliver the drilling fluid composition and prevention of gelformation in the drilling fluid composition. Improving pump-ability ofthe drilling fluid composition and, thus, reducing the pump pressureneeded to circulate the drilling fluid composition into and out of thewellbore may reduce energy costs and result in a more efficient drillingfluid circulation process.

The drilling fluid composition having the ethoxylated alcohol compoundmay also decrease the probability of causing a differentially stuck pipeby minimizing solids settling in the drilling fluid composition.Maintaining the density and yield point of the drilling fluidcomposition with the ethoxylated alcohol compound maintains thesupportive and hole-cleaning properties of the drilling fluid. Inparticular, maintaining the density may preserve the ability of thedrilling fluid composition to support the wellbore and prevent fluids inthe downhole formations from entering the wellbore. Maintaining theyield point of the drilling fluid composition maintains the ability ofthe drilling fluid composition to convey rock cuttings from the drillingzone to the top of the well-bore, which may preserve the hole-cleaningproperties of the drilling fluid composition.

Additionally, the ethoxylated alcohol compound may facilitate the use ofdrilling fluid compositions having high density and solids content fordrilling through highly pressurized formations, such as the Jilhformation in Saudi Arabia for example, and for controlling and killingformation fluids flowing into the wellbore during drilling operation.The drilling fluid composition having the ethoxylated alcohol compoundmay achieve the thinning effect without compromising other properties ofthe drilling fluid composition, such as density, hole-cleaningcapabilities, and pump-ability.

The ethoxylated alcohol compound may be used in methods for thinning adrilling fluid composition. In some embodiments, a method of thinning adrilling fluid includes adding an amount of an ethoxlylated alcoholcompound to a drilling fluid to produce a drilling fluid compositionhaving from 0.1 wt. % to 1 wt. % ethoxylated alcohol compound based onthe total weight of the drilling fluid. The drilling fluid compositioncomprises a base fluid and at least one additive chosen from anemulsifier, a weighting material, a fluid-loss additive, a viscosifier,or an alkali compound. The ethoxylated alcohol compound is a compoundhaving formula (I):

R—(OCH₂CH₂)₇—OH   (I)

where R is a saturated or unsaturated, linear or branched hydrocarbylgroup having from 8 to 20 carbon atoms. In an example method, drillingfluid composition may include from 0.1 wt. % to 1 wt. % ethoxylatedalcohol compound in embodiments, or from 0.1 wt. % to 0.8 wt. %ethoxylated alcohol compound in other embodiments, or from 0.2 wt. % to0.6 wt. % ethoxylated alcohol compound in yet other embodiments. In someexample methods for thinning a drilling fluid, the ethoxylated alcoholcompound may be added to the drilling fluid to produce the drillingfluid composition having from 0.1 wt. % to 1 wt. % ethoxylated alcoholcompound before using the drilling fluid composition in a drillingoperation to drill a subterranean well.

The drilling fluid composition that includes the ethoxylated alcoholcompound may be used for drilling a subterranean well. According toembodiments, a method of drilling a subterranean well may includeoperating a drill in a wellbore in the presence of a drilling fluidcomposition comprising a base fluid, at least one additive chosen froman emulsifier, a weighting material, a fluid-loss additive, aviscosifier, or an alkali compound, and from 0.1 wt. % to 1 wt. %, basedon the total weight of the drilling fluid composition, of an ethoxylatedalcohol compound having formula (I):

R—(OCH₂CH₂)₇—OH   (I)

where R is a saturated or unsaturated, linear or branched hydrocarbylgroup having from 8 to 20 carbon atoms. In some embodiments, thedrilling fluid composition has a yield point of from 45 lbf/100 ft²(21.6 Pa) to 100 lbf/100 ft² (48 Pa) and a 10-second gel strength offrom 1 lbf/100 ft² (0.5 Pa) to 30 lbf/100 ft² (14.4 Pa) as determinedaccording to test methods provided in API RP 13B-1 (American PetroleumInstitute Recommended Procedure 13B-1). The base fluid may be an aqueousbase fluid. In some example methods, the base fluid is an aqueous basefluid comprising at least 50 wt. % water. In some embodiments, the basefluid may be an oleaginous base fluid. In still other embodiments, thebase fluid may be an invert emulsion fluid. In example methods, thedrilling fluid composition further comprises at least one of xanthan gumpolymer, soda ash, sodium sulfite, or starch.

The methods for drilling subterranean wells may include operating adrill in a wellbore in the presence of a drilling fluid compositioncomprising: a base fluid, a solid added to the base fluid, and from 0.1wt. % to 1 wt. % of an ethoxylated alcohol compound (compound) havingthe formula R—(OCH₂CH₂)₇—OH, where R is a saturated or unsaturated,linear or branched hydrocarbyl group having from 8 to 20 carbon atoms.The drilling fluid composition has a density of greater than or equal to100 pounds per cubic foot. The drilling fluid composition used fordrilling the subterranean well may have a yield point of from 45 lbf/100ft² to 100 lbf/100 ft² and a 10-second gel strength of from 1 lbf/100ft² to 30 lbf/100 ft².

Another example method of drilling a subterranean well includesoperating a drill in a wellbore and circulating a drilling fluidcomposition through the wellbore. The drilling fluid compositionincludes a solid added to a base liquid and has a density equal to orgreater than 100 pounds per cubic foot. The method further includesadding an ethoxylated alcohol compound to the drilling fluidcomposition, the ethoxylated alcohol compound having the formula:R—(OCH₂CH₂)₇—OH, where R is a saturated or unsaturated, linear orbranched hydrocarbyl group having from 8 to 20 carbon atoms. In someexamples of the method of drilling a subterranean well, the ethoxylatedalcohol compound may be added to the drilling fluid composition beforeoperating the drill in the wellbore. In other examples of the method ofdrilling a subterranean well, the ethoxylated alcohol compound may beadded to the drilling fluid composition during operation of the drill.The ethoxylated alcohol compound may be added to a drilling fluidcomposition as a stand-alone additive, meaning no other supplementaladditives are included. For example, in some embodiments, theethoxylated alcohol compound may consist essentially of the reactionproduct of the fatty alcohol of the ethylene oxide at a 1:7 molar ratioof the fatty alcohol to the ethylene oxide and may not contain any otheradditives.

EXAMPLES

The following examples illustrate one or more additional features of thepresent disclosure described previously. It should be understood thatthese examples are not intended to limit the scope of the disclosure orthe appended claims in any manner.

In the following examples, water-based drilling fluids were preparedcontaining water, soda ash, pre-hydrated bentonite, xanthan gum polymer,starch, lime, sodium sulfite, and barite, with or without a thinner. Thedrilling fluids were formulated to have identical densities,accomplished in certain drilling fluids by slightly varying the amountsof water or barite present in the fluid. Thus, the identity of thethinner was the distinguishing characteristic used as a basis forcomparing the drilling fluids of identical densities. The identities ofthe thinners used in the various water-based drilling fluids aresummarized in Table 1. The physical characteristics of the water-baseddrilling fluids are described in Example 9 and are summarized in Tables6 and 7.

TABLE 1 Reference Table of the Thinners Used in each Example ExampleThinner 1 (Comparative) None 2 (Comparative) SPARSENE ® drilling fluidthinner available from MI SWACO, a Schlumberger Company, Houston, TexasUSA. 3 C₁₂H₂₅(OCH₂CH₂)₇OH according to embodiments of this disclosure 4(Comparative) C₁₀H₂₁(OCH₂CH₂)₇OH 5 (Comparative) C₁₂H₂₅(OCH₂CH₂)₁OH 6(Comparative) C₁₃H₂₇(OCH₂CH₂)₈OH 7 (Comparative) C₁₂H₂₅(OCH₂CH₂)₉OH 8(Comparative) C₁₃H₂₇(OCH₂CH₂)₆OH

Comparative Example 1 Water-Based Drilling Fluid with No Thinner

A water-based drilling fluid having high density and high solids contentwas formulated as a control sample for comparison with water-baseddrilling fluids containing various thinners. The water-based drillingfluid included water, soda ash, pre-hydrated bentonite, xanthan gumpolymer, starch, lime, sodium sulfite, and barite in amounts providedsubsequently in Table 2. The components of the water-based drillingfluid were added to a vessel and thoroughly mixed. The target density ofthe water-based drilling fluid formulation was 130 pounds (mass) percubic foot (lbm/ft³). The components of the water-based drilling fluidof Comparative Example 1 were added to a vessel and thoroughly mixed.

TABLE 2 Formulation for the Water-Based Drilling Fluid of ComparativeExample 1 Amount Weight Percent Ingredient (lbm/bbl) (wt. %) Water 229.4 31.47% Soda Ash 0.3  0.04% Pre-Hydrated 5  0.69% Bentonite Xanthan Gum0.35  0.05% Starch 4  0.55% Lime 0.25  0.03% Sodium Sulfite 0.25  0.03%Barite 489.38  67.14% Thinner 0  0.00% TOTAL 728.93 100.00%

Comparative Example 2 Water-Based Drilling Fluid with a CommerciallyAvailable Thinner

A water-based drilling fluid composition was formulated to include anamount of a commercially available thinner. The water-based drillingfluid composition was adjusted to compensate for the different densityof the commercially available thinner so that the water-based drillingfluid of Comparative Example 2 had the same density as the water-baseddrilling fluid of Comparative Example 1. The commercially availablethinner was SPERSENE® brand additive available from M-I SWACO, aSchlumberger company, Houston, Tex. The formulation for ComparativeExample 2 is listed in Table 3 subsequently provided in this disclosure.The components of the water-based drilling fluid of Comparative Example2, including the commercially available thinner, were added to a vesseland thoroughly mixed.

TABLE 3 Formulation for the Water-Based Drilling Fluid of ComparativeExample 2 Including the Commercially Available Thinner Amount WeightPercent Ingredient (lbm/bbl) (wt. %) Water 227.3  31.18% Soda Ash 0.3 0.04% Pre-Hydrated Bentonite 5  0.69% XC Polymer 0.35  0.05% Starch 4 0.55% Lime 0.25  0.03% Sodium Sulfite 0.25  0.03% Barite 488.48  67.01%Thinner 3  0.41% TOTAL 728.93 100.00%

Example 3 Water-Based Drilling Fluid Composition With C₁₂H₂₅(OCH₂CH₂)₇OHEthoxylated Alcohol Compound

A water-based drilling fluid composition was prepared to include anamount of an ethoxylated alcohol compound according to embodiments ofthe present disclosure. The ethoxylated alcohol compound had thechemical formula CH₃(CH₂)₁₁(OCH₂CH₂)₇OH. The water-based drilling fluidcomposition of Example 3 was adjusted to compensate for the differentdensity of the ethoxylated alcohol compound so that the water-baseddrilling fluid composition had the same density as the water-baseddrilling fluids of Comparative Examples 1 and 2. The components of thewater-based drilling fluid composition of Example 3, including theethoxylated alcohol compound, were added to a vessel and thoroughlymixed. The formulation for the water-based drilling fluid composition ofExample 3 is listed in Table 4 subsequently provided.

TABLE 4 Formulation for the Water-Based Drilling Fluid Composition ofExample 3 Having C₁₂H₂₅(OCH₂CH₂)₇OH Ethoxylated Alcohol Compound AmountWeight Percent Ingredient (lbm/bbl) (wt. %) Water 226.36  31.05% SodaAsh 0.3  0.04% Pre-Hydrated 5  0.69% Bentonite XC Polymer 0.35  0.05%Starch 4  0.55% Lime 0.25  0.03% Sodium Sulfite 0.25  0.03% Barite489.42  67.14% Thinner 3  0.41% TOTAL 728.93 100.00%

Comparative Examples 4-8 Water-Based Drilling Fluids With OtherEthoxylated Alcohol Compounds

For comparison with the water-based drilling fluid composition ofExample 3 having the ethoxylated fatty alcohol thinnerC₁₂H₂₅(OCH₂CH₂)₇OH, five alternative water-based drilling fluidcompositions having the alternative ethoxylated alcohols listed in Table1 were prepared. Each of the water-based drilling fluid compositions ofComparative Examples 4-8 was prepared to include a different alternativeethoxylated alcohol compound. Each of the water-based drilling fluidcompositions of Comparative Examples 4-8 exhibited the same density asthe water-based drilling fluid compositions of Comparative Examples 1,Comparative Example 2, and Example 3. For each formulation of thewater-based drilling fluid compositions of Comparative Examples 4-8, thecomponents of the water-based drilling fluid composition were added to avessel and thoroughly mixed. The water-based drilling fluid compositionsof Comparative Examples 4-8 along with the water-based drilling fluidcomposition of Example 3 are listed in Table 5 subsequently provided.Table 5 also includes the total amount of each of the water-baseddrilling fluid compositions were prepared.

TABLE 5 Water-Based Drilling Fluid Formulations for Comparative Examples4-8 and Example 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 3 (comparative)(comparative) (comparative) (comparative) (comparative) lbm/bbl lbm/bbllbm/bbl lbm/bbl lbm/bbl lbm/bbl Ingredient (wt. %) (wt. %) (wt. %) (wt.%) (wt. %) (wt. %) Water 226.36   226.36   226.36   226.36   226.36  226.36    (31.05%)  (31.05%)  (31.05%)  (31.05%)  (31.05%)  (31.05%)Soda Ash 0.3  0.3  0.3  0.3  0.3  0.3   (0.04%)  (0.04%)  (0.04%) (0.04%)  (0.04%)  (0.04%) Pre-Hydrated 5  5  5  5  5  5  Bentonite (0.69%)  (0.69%)  (0.69%)  (0.69%)  (0.69%)  (0.69%) XC Polymer  0.35 0.35  0.35  0.35  0.35  0.35  (0.05%)  (0.05%)  (0.05%)  (0.05%) (0.05%)  (0.05%) Starch 4  4  4  4  4  4   (0.55%)  (0.55%)  (0.55%) (0.55%)  (0.55%)  (0.55%) Lime  0.25  0.25  0.25  0.25  0.25  0.25 (0.03%)  (0.03%)  (0.03%)  (0.03%)  (0.03%)  (0.03%) Sodium  0.25  0.25 0.25  0.25  0.25  0.25 Sulfite  (0.03%)  (0.03%)  (0.03%)  (0.03%) (0.03%)  (0.03%) Barite 489.42   489.42   489.42   489.42   489.42  489.42    (67.14%)  (67.14%)  (67.14%)  (67.14%)  (67.14%)  (67.14%)Thinner 3  3  3  3  3  3   (0.41%)  (0.41%)  (0.41%)  (0.41%)  (0.41%) (0.41%) TOTAL 728.93   728.93   728.93   728.93   728.93   728.93  (100.00%) (100.00%) (100.00%) (100.00%) (100.00%) (100.00%)

Example 9 Characterizations of Water-Based Drilling Fluid Compositions

The water-based drilling fluid compositions of Comparative Example 1,Comparative Example 2, and Example 3 were evaluated for viscosity, gelstrength, PV, YP, pH, and density according to the methods previouslydescribed in this disclosure. The results of these evaluations for thewater-based drilling fluid compositions of Comparative Example 1,Comparative Example 2, and Example 3 are provided subsequently in Table6. Table 6 also includes a calculated change in the 10-second gelstrength, 10-minute gel strength, PV, and YP of the water-based drillingfluid compositions of Comparative Example 2 and Example 3 compared tothe water-based drilling fluid composition of Comparative Example 1.

TABLE 6 Evaluation of the Properties of the Water-Based Drilling FluidCompositions of Comparative Example 1, Comparative Example 2, andExample 3 Example 1 Example 2 (comparative) (comparative) Example 3Thinner None SPERSENE ® C₁₂H₂₅(OCH₂CH₂)₇OH Shear Stress at 189 165 177600 rpm (lbf/100 ft²) Shear Stress at 126 102 116 300 rpm (lbf/100 ft²)Shear Stress at 102 77.5 92 200 rpm (lbf/100 ft²) Shear Stress at 7349.5 65 100 rpm (lbf/100 ft²) Shear Stress at 40 14.5 26 6 rpm (lbf/100ft²) Shear Stress at 39 10.5 23 3 rpm (lbf/100 ft²) 10-second Gel 36 9.512 Strength (lbf/100 ft²) 10-Minute Gel 75 38 42 Strength (lbf/100 ft²)PV (cP) 63 63 61 YP 63 39 55 (lbf/100 ft²) pH 10.57 9.76 9.8 Change in —−74 −67 10-second Gel Strength (%) Change in — −49 −44 10-Minute GelStrength (%) Change in PV — 0 −3 (%) Change in YP — −38 −13 (%)

As shown in Table 6, inclusion of the commercially available thinner inthe drilling fluid of Comparative Example 2 resulted in a 74% reductionin the 10-second gel strength of the drilling fluid and a 49% reductionin the 10 minute gel strength of the drilling fluid compared to thedrilling fluid composition of Comparative Example 1. The PV of thedrilling fluid composition of Comparative Example 2 was the same as thePV of the drilling fluid composition of Comparative Example 1; however,the drilling fluid composition of Comparative Example 2 exhibited a 38%reduction in the YP compared to the drilling fluid composition ofComparative Example 1. Although the drilling fluid composition havingthe commercially available thinner of Comparative Example 2 exhibited areduced gel strength compared to the drilling fluid composition ofComparative Example 1, the drilling fluid composition having thecommercially available thinner showed a significant reduction of 38% inthe YP, which substantially reduces the ability of the drilling fluidcomposition of Comparative Example 2 to capture and convey rock cuttingsto the surface.

As shown in Table 6, the drilling fluid composition of Example 3, whichincluded the ethoxylated alcohol compound C₁₂H₂₅(OCH₂CH₂)₇OH, resultedin a 67% reduction in the 10-second gel strength and a 44% reduction inthe 10-minute gel strength of the drilling fluid compared to thedrilling fluid composition of Comparative Example 1. The reduction ingel strength achieved by the drilling fluid composition having theethoxylated alcohol compound of Example 3 was slightly less than, butcomparable to, the drilling fluid having the commercially availablethinner of Comparable Example 2. The drilling fluid composition havingthe ethoxylated alcohol compound of Example 3 exhibited a slight 3%reduction in the PV of the drilling fluid compared to the drillingfluids of Comparative Example 1 and Comparative Example 2. The drillingfluid composition having the ethoxylated alcohol compound of Example 3showed only a 13% reduction in YP of the drilling fluid composition ofExample 3 compared to the drilling fluid composition of ComparativeExample 1.

The purpose of incorporating the ethoxylated alcohol compound of Example3 or the commercially available thinner of Comparative Example 2 is toreduce the plastic viscosity and gel strength of the drilling fluidcomposition. The drilling fluid compositions having the ethoxylatedalcohol compound of Example 3 performed equivalent to the drillingfluids having the commercially available thinner of Comparative Example2 with respect to reduced PV and gel strength. The deflocculant orthinning effect of the drilling fluid composition having the ethoxylatedalcohol compound of Example 3, therefore, is equivalent to that of thedrilling fluid composition having the commercially available thinner ofComparative Example 2 as shown by the similar effect on PV and gelstrength.

However, the drilling fluid composition having the ethoxylated alcoholcompound of Example 3 better maintains the YP of the drilling fluidcomposition compared to the drilling fluid having the commerciallyavailable thinner of Comparative Example 2. The drilling fluid havingthe commercially available thinner of Comparative Example 2 exhibited ina 38% reduction in the YP of the water-based drilling fluid ofComparative Example 2 compared with the water-based drilling fluid ofComparative Example 1, which had no thinner. In contrast, the drillingfluid composition having the ethoxylated alcohol compound of Example 3exhibited only a 13% reduction in the YP of the water-based drillingfluid composition of Example 3 compared to the water-based drillingfluid of Comparative Example 1, which had no thinner. The YP relates tothe ability of the drilling fluid composition to convey rock cuttings tothe surface and, thus, the hole-cleaning properties of the drillingfluid composition. The drilling fluid composition having the ethoxylatedalcohol compound of Example 3 resulted in less of a reduction in the YPof the drilling fluid composition compared to the drilling fluids havingthe commercially available thinner of Comparative Example 2. Thus, thedrilling fluid composition having the ethoxylated alcohol compound ofExample 3 outperformed the drilling fluid composition having thecommercially available thinner of Comparative Example 2 with respect tomaintaining the YP of drilling fluid composition, and consequentlymaintaining the ability of the drilling fluid composition to capture andconvey rock cuttings to the surface of the wellbore (hole-cleaningability).

To summarize, the PV and gel strength performance of the drilling fluidcompositions having the ethoxylated alcohol compound of Example 3provides equivalent reduction in gel strength and enhanced pump-abilityof the water-based drilling fluid composition compared to the drillingfluid having the commercially available thinner of Comparative Example2, and the superior YP performance of the drilling fluid compositionhaving the ethoxylated alcohol compound of Example 3 compared to thedrilling fluid having the commercially available thinner of ComparativeExample 2 preserves the hole-cleaning properties of the water-baseddrilling fluid composition. Therefore, the presence of the ethoxylatedalcohol compound in the drilling fluid composition, as in Example 3,reduces the gel strength of and enhances the pump-ability of thedrilling fluid composition without jeopardizing the hole-cleaningproperties of the drilling fluid composition.

The water-based drilling fluid compositions of Comparative Examples 4-8were also evaluated for viscosity, gel strength, PV, YP, pH, and densityaccording to the methods previously described in this disclosure. Theresults of these evaluations for the water-based drilling fluidcompositions of Comparative Examples 4-8, as well as the results forComparative Example 1 and Example 3, are provided subsequently in Table7. Table 7 also includes a calculated change in the 10-second gelstrength, 10-minute gel strength, PV, and YP of the water-based drillingfluid compositions of Comparative Examples 4-8 and Example 3 compared tothe water-based drilling fluid composition of Comparative Example 1.

TABLE 7 Evaluation of the Properties of the Water-Based Drilling FluidCompositions of Comparative Example 1, Example 3, and ComparativeExamples 4-8 Ex. 1 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 comparative Ex. 3comparative comparative comparative comparative comparative Shear 189177  192    250  180  188  167  Stress at 600 rpm (lbf/100 ft²) Shear126 116  130    193  125  127  115  Stress at 300 rpm (lbf/100 ft²)Shear 102 92 105    170  103  102  95   Stress at 200 rpm (lbf/100 ft²)Shear 73 65 74   139  76 72 71   Stress at 100 rpm (lbf/100 ft²) Shear40 26 46   105  33 42 36   Stress at 6 rpm (lbf/100 ft²) Shear 39 2342   101  30 40 34   Stress at 3 rpm (lbf/100 ft²) 10-second 36 12 40  96 31 35 33   Gel Strength (lbf/100 ft²) 10-Minute 75 42 85   127  62 5676   Gel Strength (lbf/100 ft²) PV (cP) 63 61 62   57 55 61 61   YP 6355 68   136  70 66 66   (lbf/100 ft²) pH 10.57   9.8  9.7  9.7  9.9  9.912.1 Change in — −67% 11% 167% −14%  −3% −8% 10-second Gel Strength (%)Change in — −44% 13%  69% −17% −25%  1% 10-Minute Gel Strength (%)Change in —  −3% −2% −10% −13%  −3% −3% PV (%) Change in — −13%  8% 116% 11%   5%  5% YP (%)

As shown in Table 7, drilling fluid compositions of Comparative Examples6-8 exhibited reductions in the gel strength of the drilling fluidcomposition compared to the drilling fluid of Comparative Example 1,which did not include a thinner. However, these reductions in gelstrength for Comparative Examples 6-8 relative to Comparative Example 1were significantly less than the reduction in gel strength of thedrilling fluid composition of Example 3 relative to ComparativeExample 1. Out of Comparative Examples 6-8, the best performing drillingfluid composition was Comparative Example 6, which exhibited a 14%reduction in the 10-second gel strength and a 17% reduction in the10-minute gel strength compared to the drilling fluid composition ofComparative Example 1. As previously described, the drilling fluidcomposition including the ethoxylated alcohol compound of Example 3resulted in greater reductions in the gel strength of the drilling fluidcomposition (67% reduction in 10-second gel strength and a 44% reductionin the 10-minute gel strength compared to the drilling fluid compositionof Comparative Example 1) as compared to the drilling fluid compositionsof Comparative Examples 4-8. For Comparative Examples 4 and 5, the10-second gel strength and the 10-minute gel strength of the drillingfluid compositions actually increased compared to the drilling fluidcomposition of Comparative Example 1, which did not contain a thinner.

A first aspect of the present disclosure may be directed to a drillingfluid composition comprising a base fluid; at least one additive chosenfrom an emulsifier, a weighting material, a fluid-loss additive, aviscosifier, or an alkali compound; and from 0.1 wt. % to 1 wt. %, basedon the total weight of the drilling fluid composition, of an ethoxylatedalcohol compound having formula (I):

R—(OCH₂CH₂)₇—OH   (I)

where R is a hydrocarbyl group having from 8 to 20 carbon atoms.

A second aspect of the present disclosure may include the first aspect,where the drilling fluid composition has a yield point of from 45lbf/100 ft² to 100 lbf/100 ft² and a 10-second gel strength of from 1lbf/100 ft² to 30 lbf/100 ft² as determined according to test methodsprovided in API RP 13B-1.

A third aspect of the present disclosure may include the first andsecond aspects, in which the base fluid is an aqueous base fluid.

A fourth aspect of the present disclosure may include the third aspect,in which the aqueous base fluid comprises at least 50 weight percentwater based on the total weight of the aqueous base fluid.

A fifth aspect of the present disclosure may include the third andsecond aspects, in which the aqueous base fluid is chosen from freshwater, filtered water, distilled water, sea water, salt water, producedwater, formation brine, or combinations thereof.

A sixth aspect of the present disclosure may include the first throughfifth aspects, in which R is a saturated linear hydrocarbyl group.

A seventh aspect of the present disclosure may include the first throughsixth aspects, in which R is —(CH₂)_(m)CH₃, where m is 11, 12, or 13.

An eighth aspect of the present disclosure may include the first throughsixth aspects, in which R has exactly 12 carbon atoms.

A ninth aspect of the present disclosure may include the first througheighth aspects, in which the drilling fluid composition has a density ofequal to or greater than 70 lbm/ft³.

A tenth aspect of the present disclosure may include the first throughninth aspects, in which the at least one additive comprises a weightingmaterial.

An eleventh aspect of the present disclosure may include the tenthaspect, in which the weighting material is chosen from at least one ofbarite, calcium carbonate, hematite, siderite, or ilmenite.

A twelfth aspect of the present disclosure may include the tenth andeleventh comprising from 1 wt. % to 73 wt. % weighting material, basedon the total weight of the drilling fluid composition.

A thirteenth aspect of the present disclosure may include the firstthrough twelfth aspects comprising from 20 wt. % to 50 wt. % base fluid,based on the total weight of the drilling fluid composition.

A fourteenth aspect of the present disclosure may include the firstthrough thirteenth aspects further comprising from 0.01 wt. % to 0.7 wt.% xanthan gum polymer based on the total weight of the drilling fluidcomposition.

A fifteenth aspect of the present disclosure may include the firstthrough fourteenth aspects further comprising from 0.01 wt. % to 0.7 wt.% soda ash based on the total weight of the drilling fluid composition.

A sixteenth aspect of the present disclosure may include the firstthrough fifteenth aspects further comprising from 0.01 wt. % to 3.0 wt.% sodium sulfite based on the total weight of the drilling fluidcomposition.

A seventeenth aspect of the present disclosure may include the firstthrough sixteenth aspects further comprising from 0.1 wt. % to 1 wt. %starch based on the total weight of the drilling fluid composition.

An eighteenth aspect of the present disclosure may include the firstthrough seventeenth aspects, in which the at least one additivecomprises a weighting material, and in which the drilling fluidcomposition comprises, based on the total weight of the drilling fluidcomposition: from 1 wt. % to 73 wt. % weighting material, from 0.01 wt.% to 0.7 wt. % soda ash, from 0.01 wt. % to 3 wt. % pre-hydratedbentonite, from 0.01 wt. % to 0.7 wt. % xanthan gum polymer, from 0.1wt. % to 1.0 wt. % starch, from 0.01 wt. % to 3 wt. % lime, and from0.01 wt. % to 3 wt. % sodium sulfite.

A nineteenth aspect of the present disclosure may be directed to amethod of drilling a subterranean well, the method comprising operatinga drill in a wellbore in the presence of a drilling fluid compositioncomprising: a base fluid; at least one additive chosen from anemulsifier, a weighting material, a fluid-loss additive, a viscosifiers,or an alkali compound; and from 0.1 wt. % to 1 wt. %, based on the totalweight of the drilling fluid composition, of an ethoxylated alcoholcompound having formula (I):

R—(OCH₂CH₂)₇—OH   (I)

where R is a hydrocarbyl group having from 8 to 20 carbon atoms.

A twentieth aspect of the present disclosure may include the nineteenthaspect, in which the drilling fluid composition has a yield point offrom 45 lbf/100 ft² to 100 lbf/100 ft² and a 10-second gel strength offrom 1 lbf/100 ft² to 30 lbf/100 ft² as determined according to testmethods provided in API RP 13B-1.

A twenty-first aspect of the present disclosure may include thenineteenth and the twentieth aspects, in which the base fluid is anaqueous base fluid.

A twenty-second aspect of the present disclosure may include thetwenty-first aspect, in which the aqueous base fluid comprises at least50 weight percent water based on the total weight of the aqueous basefluid.

A twenty-third aspect of the present disclosure may include thetwenty-first and twenty-second aspects, in which the aqueous base fluidis chosen from fresh water, filtered water, distilled water, sea water,salt water, produced water, formation brine, or combinations thereof.

A twenty-fourth aspect of the present disclosure may include theninteenth through twenty-third aspects, in which R is a saturated linearhydrocarbyl group.

A twenty-fifth aspect of the present disclosure may include theninteenth through twenty-fourth aspects, in which R is —(CH₂)_(m)CH₃,where m is 11, 12, or 13.

A twenty-sixth aspect of the present disclosure may include theninteenth through twenty-fourth aspects, in which R has exactly 12carbon atoms.

A twenty-seventh aspect of the present disclosure may include theninteenth through twenty-sixth aspects, in which the drilling fluidcomposition has a density of equal to or greater than 70 lbm/ft³.

A twenty-eighth aspect of the present disclosure may include theninteenth through twenty-seventh aspects, in which the one or moreadditives comprise a weighting material.

A twenty-ninth aspect of the present disclosure may include thetwenty-eighth aspect, in which the weighting material comprises at leastone of barite, calcium carbonate, hematite, siderite, or ilmenite.

A thirtieth aspect of the present disclosure may include thetwenty-eighth and twenty-ninth aspects, in which the drilling fluidcomposition comprises from 1 wt. % to 73 wt. % weighting material basedon the total weight of the drilling fluid composition.

A thirty-first aspect of the present disclosure may include thenineteenth through thirtieth aspects, in which the drilling fluidcomposition comprises from 20 wt. % to 50 wt. % base fluid, based on thetotal weight of the drilling fluid composition.

A thirty-second aspect of the present disclosure may include thenineteenth through thirty-first aspects, in which the drilling fluidcomposition further comprises at least one of a xanthan gum polymer,soda ash, sodium sulfite, or starch.

A thirty-third aspect of the present disclosure may include thenineteenth through thirty-second aspects, further comprising adding thecompound having formula (I) to the drilling fluid composition before orduring operating the drill in the wellbore.

A thirty-fourth aspect of the present disclosure may include thenineteenth through thirty-third aspects, in which the compound havingformula (I) is added to the drilling fluid composition during operationof the drill in the wellbore.

It is noted that one or more of the following claims utilize the term“where” or “in which” as a transitional phrase. For the purposes ofdefining the present technology, it is noted that this term isintroduced in the claims as an open-ended transitional phrase that isused to introduce a recitation of a series of characteristics of thestructure and should be interpreted in like manner as the more commonlyused open-ended preamble term “comprising.” For the purposes of definingthe present technology, the transitional phrase “consisting of” may beintroduced in the claims as a closed preamble term limiting the scope ofthe claims to the recited components or steps and any naturallyoccurring impurities. For the purposes of defining the presenttechnology, the transitional phrase “consisting essentially of” may beintroduced in the claims to limit the scope of one or more claims to therecited elements, components, materials, or method steps as well as anynon-recited elements, components, materials, or method steps that do notmaterially affect the novel characteristics of the claimed subjectmatter. The transitional phrases “consisting of” and “consistingessentially of” may be interpreted to be subsets of the open-endedtransitional phrases, such as “comprising” and “including,” such thatany use of an open ended phrase to introduce a recitation of a series ofelements, components, materials, or steps should be interpreted to alsodisclose recitation of the series of elements, components, materials, orsteps using the closed terms “consisting of” and “consisting essentiallyof.” For example, the recitation of a composition “comprising”components A, B, and C should be interpreted as also disclosing acomposition “consisting of” components A, B, and C as well as acomposition “consisting essentially of” components A, B, and C. Anyquantitative value expressed in the present application may beconsidered to include open-ended embodiments consistent with thetransitional phrases “comprising” or “including” as well as closed orpartially closed embodiments consistent with the transitional phrases“consisting of” and “consisting essentially of.”

It should be understood that any two quantitative values assigned to aproperty may constitute a range of that property, and all combinationsof ranges formed from all stated quantitative values of a given propertyare contemplated in this disclosure. The subject matter of the presentdisclosure has been described in detail and by reference to specificembodiments. It should be understood that any detailed description of acomponent or feature of an embodiment does not necessarily imply thatthe component or feature is essential to the particular embodiment or toany other embodiment. Further, it should be apparent to those skilled inthe art that various modifications and variations can be made to thedescribed embodiments without departing from the spirit and scope of theclaimed subject matter.

What is claimed is:
 1. A drilling fluid composition consistingessentially of: a base fluid; at least one additive chosen from anemulsifier, a weighting material, a fluid-loss additive, a viscosifier,or an alkali compound; and from 0.1 wt. % to 1 wt. %, based on the totalweight of the drilling fluid composition, of an ethoxylated alcoholcompound having formula (I):R—(OCH₂CH₂)₇—OH   (I)  where R is a hydrocarbyl group having exactly 12carbon atoms; in which the drilling fluid composition has a densityequal to or greater than 90 lbm/ft³.
 2. The drilling fluid compositionof claim 1 where the drilling fluid composition has a yield point offrom 45 lbf/100 ft² to 100 lbf/100 ft² and a 10-second gel strength offrom 1 lbf/100 ft² to 30 lbf/100 ft² as determined according to testmethods provided in API RP 13B-1.
 3. The drilling fluid composition ofclaim 1, in which the base fluid is an aqueous base fluid.
 4. Thedrilling fluid composition of claim 3, in which the aqueous base fluidcomprises at least 50 weight percent water based on the total weight ofthe aqueous base fluid.
 5. The drilling fluid composition of claim 3, inwhich the aqueous base fluid is chosen from fresh water, filtered water,distilled water, sea water, salt water, produced water, formation brine,or combinations thereof.
 6. The drilling fluid composition of claim 1,in which R is a saturated linear hydrocarbyl group.
 7. The drillingfluid composition of claim 1, in which R is —(CH₂)_(m)CH₃, where m is11.
 10. The drilling fluid composition of claim 1, in which the at leastone additive comprises a weighting material.
 11. The drilling fluidcomposition of claim 10, in which the weighting material is chosen fromat least one of barite, calcium carbonate, hematite, siderite, orilmenite.
 12. The drilling fluid composition of claim 10 comprising from1 wt. % to 73 wt. % weighting material, based on the total weight of thedrilling fluid composition.
 13. The drilling fluid composition of claim1 comprising from 20 wt. % to 50 wt. % base fluid, based on the totalweight of the drilling fluid composition.
 14. The drilling fluidcomposition of claim 1 further comprising from 0.01 wt. % to 0.7 wt. %xanthan gum polymer based on the total weight of the drilling fluidcomposition.
 15. The drilling fluid composition of claim 1 furthercomprising from 0.01 wt. % to 0.7 wt. % soda ash based on the totalweight of the drilling fluid composition.
 16. The drilling fluidcomposition claim 1, in which the at least one additive consistsessentially of a weighting material, and in which the drilling fluidcomposition comprises, based on the total weight of the drilling fluidcomposition: from 1 wt. % to 73 wt. % weighting material; from 0.01 wt.% to 0.7 wt. % soda ash; from 0.01 wt. % to 3 wt. % pre-hydratedbentonite; from 0.01 wt. % to 0.7 wt. % xanthan gum polymer; from 0.1wt. % to 1.0 wt. % starch; from 0.01 wt. % to 3 wt. % lime; and from0.01 wt. % to 3 wt. % sodium sulfite.